Switching controllers can be used in direct-current to direct-current (DC to DC) converters to control output of the DC to DC converters. A circuit diagram of a conventional switching controller 102 for a DC to DC converter 100 is illustrated in FIG. 1. As shown in FIG. 1, the controller 102 includes a pulse-width modulation (PWM) signal generator 104 and an operational transconductance amplifier (OTA) 106.
The PWM signal generator 104 generates a PWM signal to turn on or off switches 110 and 112, so as to adjust the output voltage VOUT of the DC to DC converter 100. The output voltage VOUT can be determined by the duty cycle of the PWM signal. In addition, the PWM signal generator 104 receives a voltage V116 on a capacitor 116 to control the duty cycle of the PWM signal. The OTA 106 compares a reference voltage VR with a feedback voltage VF that is proportional to the output voltage VOUT to control charging and discharging of the capacitor 116, and therefore to control the voltage V116. If the feedback voltage VF is less than the reference voltage VR, the OTA 106 controls the voltage V116 such that the output voltage VOUT increases. If the feedback voltage VF is greater than the reference voltage VR, the OTA 106 controls the voltage V116 such that output voltage VOUT decreases. As a result, the output voltage VOUT can be adjusted to a preset level that is determined by the reference voltage VR.
However, the bandwidth of the amplification circuit that includes the OTA 106 and the capacitor 116 may not be wide enough, such that the speed for the voltage V116 to respond to the output voltage VOUT can be relatively slow. In other words, the controller 102 may take a relatively long time to vary the duty cycle of the PWM signal in response to a change in the output voltage VOUT.
A conventional method to increase the response speed of the amplification circuit includes widening the bandwidth of the amplification circuit. However, when the bandwidth of the amplification circuit is widened, more noises may be transferred into the controller 102. The controller may be sensitive to undesired noises in the output voltage VOUT, and therefore the output voltage VOUT may not be stable. A conventional solution is to reduce the gain of the amplification circuit in exchange for enhancing the stability of the output voltage VOUT. However, if the gain of the amplification circuit decreases, the accuracy of the output voltage VOUT is adversely affected.